1. The Field of the Invention
The present invention relates to the use of magnetites and magnetic separation to bind and remove heavy metals from water. More specifically, the present invention relates to binding heavy metals in water to magnetite and then removing those bound heavy metals from the water by magnetic separation. In one aspect of the invention the heavy metal-containing magnetite is removed from the water by flowing the water past a solid matrix displaying remnant magnetism.
2. The Relevant Technology
Water pollution is a serious problem in the United States and throughout the world. In the last several decades water pollution has been the subject of increased government scrutiny and regulation. In response to the need for clean drinking water and the need to maintain clean water in rivers, lakes, oceans, and wet lands, detailed statutory and regulatory schemes have been developed at the state and local levels in the United States. These statutory and regulatory schemes relate to many types of activities that can produce water pollution. Such activities include everything from controlling the quality of run off from farming operations and in storm drainage systems, to the regulation of industrial, mining, and commercial activities. Almost any activity that produces or has the capability of producing significant quantities of tainted water will be regulated by state and federal regulations. Several regulatory agencies deal extensively with the regulation of water emissions. Some of these agencies include the United States Environmental Protection Agency (EPA) which has broad regulatory authority, the United States Coast Guard which regulates the use of navigable waters, state Oil and Gas Boards which regulate produced waters at well sites, and state and federal agencies dealing with mine regulation.
Various water pollutants, and specific activities which have the capability of producing water pollution, are the subject of water quality regulations. Materials that may be regulated range from pesticides and fertilizers, to oil and numerous chemicals and hazardous materials. Any material that may arguably be detrimental if placed in the water supplies of the nation are subject to regulation and controlled emission.
Heavy metals are one class of problematic water pollutant which is encountered widely in the environment. Essentially all transition metals can exist as dissolved ions in water. Examples of heavy metals which may become water pollutants include lead, manganese, cobalt, cadmium, and others. These materials present significant water pollution problems when they exist in a stream or water supply. Consuming water containing heavy metals is detrimental to the health of humans and animals alike. Heavy metal poisoning can be a serious public health issue. Accordingly, there is significant interest in removing heavy metals from water supplies.
At the same time, removal of heavy metals from water in bulk is a difficult and expensive process. While the chemistry of heavy metals is well understood, applying that chemistry to remove heavy metals from water in the environment and at ambient conditions has proven difficult and expensive. These processes often require large bulky processing facilities and can produce waste products which are themselves hazardous and pose difficult disposal issues.
Adding to the problem is that fact that some old industrial and mining operations have produced heavy metal emissions over many decades and in some cases for more than a century. Many of these operations pre-date modern water pollution control regulation and the development of modern water pollution control technology. Thus, these operations produced heavy metal emissions with not much effort directed to removal of the metals from the water or limitation of the pollutants prior to their release into the environment.
Where these types of facilities have continued in operation, they have been brought up to standards by the application of the necessary modifications as required by the regulatory schemes mentioned above. However, in cases where mines and other industrial facilities closed down prior to the implementation of pollution control systems and technology and the implementation of modem regulatory schemes, it is quite possible for such facilities to continue to produce water emissions tainted by heavy metals.
This is particularly true of mining operations which may have ground water flowing through them and exits into local streams and drinking water. Heavy metal contamination of natural water sources continues to be a problem in the mining communities long after mining has ceased. Due to the undesirability of heavy metal pollution in the water, much effort and expense is necessary to remediate these problems, often with less than adequate results.
Many problems exist with traditional heavy metal or water treatment remediation methods. As mentioned above, the chemistry of the metals involved is well known, so the various known processes are documented. One such method is metal hydroxide precipitation to remove heavy metals; however, this and many other conventional methods involve adding large quantities of chemicals to the waste stream which might contain quantities of contaminants at levels less than parts per thousand. These types of procedures can result in large quantities of metal-contaminated or metal-containing precipitate. As mentioned above, the disposal of the resultant metal-laden precipitate presents disposal problems of its own, particularly if the precipitate has the potential of later leaching of metals back into the environment.
Most of the known processes require complex and bulky equipment. These processes are expensive and sometimes result in less than adequate cleaning of the water. Conventional processes often result in a waste material that itself is hazardous and must be disposed of using expensive techniques which are the subject of further EPA regulation.
Thus, it would be a significant advancement in the art to provide improved methods and apparatus for cleaning water. More particularly, it would be a significant advancement in the art to provide such methods and apparatus which were capable of removing heavy metals from water. It would be an advancement in the art to provide such methods and apparatus which were capable of removing heavy metals from water without the use of chemical additives that produce large quantities of unstable chemical sludge. It would be a further advancement in the art to provide such methods and apparatus that operated using facilities significantly smaller than conventional water treatment facilities. It would be an advancement in the art to provide such methods and apparatus which were less costly to operate than conventional apparatus, and which were capable of producing waste products that were not themselves hazardous.